1. Technical Field
The technical field relates to rotary switches used mainly for operating various electronic apparatuses inside cabins of motor vehicles.
2. Background Art
In recent years, the number of rotary switches mounted to front panels and areas in the proximity of steering wheels in motor vehicles has increased. Such switches permit users to perform various controls of the vehicles, and operate various electronic apparatuses inside the vehicles. Referring to FIG. 7 to FIG. 9, description is provided of one such type of conventional rotary switches. FIG. 7 is a cross-sectional view of a conventional rotary switch, and FIG. 8 is an exploded perspective view of the rotary switch. FIG. 9 is a perspective view of the rotary switch.
Operating body 1 has operating knob 1A formed into generally a rectangular parallelepiped shape on the upper side, and cylinder portion 1B of generally a cylindrical shape on the lower side thereof. Decorative cover 2 has generally a U-shape in the top view, and is metal-plated to provide a silver finish, for instance, on the surface. Decorative cover 2 is bonded to the outer periphery of operating knob 1A with an adhesive or the like material.
Rotary body 3 has upper cylinder portion 3A of generally a cylindrical shape on the upper part, and shaft portion 3B of generally a cylindrical shape extending downward from the lower surface at the center thereof. Upper cylinder portion 3A is placed inside cylinder portion 1B of operating body 1. Upper cylinder portion 3A includes projections provided around an outer periphery thereof to engage individually with holes in a side surface of cylinder portion 1B. Rotary body 3 is attached to operating body 1 in a manner as described above.
Case 4 of generally a box-like shape has hollow tube-shaped support portion 4A formed in the substantial center thereof. Support portion 4A includes shaft portion 3B of rotary body 3 inserted therein so that rotary body 3 is rotatably supported inside case 4.
Pin 5 and coil spring 6 are placed in a predetermined position inside case 4. The tip end of pin 5 being thrust upward by coil spring 6 contacts elastically with cam portion 3C having a series of projections and depressions formed on generally same radius on the lower surface of rotary body 3. These components compose a tactile-click producing unit. This tactile-click producing unit allows rotary body 3 to be rotatable relative to case 4 while producing tactile responses, and also holds rotary body 3 at any given position of the rotation.
Wiring board 7 has conductive patterns and the like formed on both upper and lower surfaces. Light-emitting elements such as light-emitting diodes (“LED”) and the like components are mounted on the upper surface, and fixed contacts (not shown) are formed on the lower surface. Wiring board 7 is fixed to the lower surface of case 4.
Contact piece 9 made of an elastic metal plate is fixed to an upper surface of movable body 8, which is then fixed to rotary body 3 near the bottom end of shaft portion 3B that penetrates through support portion 4A. A contact portion of contact piece 9 is in contact elastically with one of the fixed contacts on the lower surface of wiring board 7. Switching unit is thus composed.
Shaft hole 10A in the substantial center of bottom cover 10 covers the bottom side of case 4. Rotary body 3 is clamped with retaining ring 11 fitted into groove 3D in the lower end of shaft portion 3B that penetrates through shaft hole 10A, thereby preventing shaft portion 3B from coming off upward.
Top cover 12 covers an opening of case 4 around operating body 1, and it is fixed securely to case 4. Rotary switch 20 shown in FIG. 9 is constructed as discussed above.
When assembling rotary switch 20, the first step is to apply an adhesive to operating knob 1A, place decorative cover 2 thereon, and harden the adhesive to complete bonding of decorative cover 2 to operating body 1.
Next, rotary body 3 is attached to the underside of operating body 1, and shaft portion 3B is inserted in support portion 4A of case 4 in which pin 5 and coil spring 6 are set in their positions. Thereafter, top cover 12 is placed on case 4, and is fixed to case 4 with operating knob 1A of operating body 1 protruding above top cover 12.
Furthermore, shaft portion 3B is inserted into hole 7A at the center substantial of wiring board 7, and wiring board 7 is placed to the underside of case 4. After that, shaft portion 3B is inserted into hole 8A of movable body 8 provided with contact piece 9 so that the contact portion of contact piece 9 comes into elastic contact with any of the fixed contacts on the lower surface of wiring board 7.
Then, shaft portion 3B is inserted into hole 10A of bottom cover 10, bottom cover 10 is placed under movable body 8, and bottom cover 10 and wiring board 7 are fixed to case 4 with a plurality of screws (not shown). Finally, retaining ring 11 is fixed by being clamped in groove 3D in the lower end of shaft portion 3B, thus completing assembly of rotary switch 20.
Rotary switch 20 is mounted to a front panel or an area in the proximity of a steering wheel in a motor vehicle. The switching unit is electrically connected to an electronic circuit (not shown) in the motor vehicle via the conductive patterns on wiring board 7, connectors, lead wires and the like (not shown).
In the structure described above, when operating knob 1A is turned clockwise from the position shown in FIG. 9, operating body 1 rotates with tactile responses produced by the tactile-click producing unit until operating body 1 is held at a predetermined position of the rotation. This causes the switching unit to make and break electrical continuity by moving of shaft portion 3B of rotary body 3 and movable body 8 mounted to shaft portion 3B. The electronic circuit of the motor vehicle controls various apparatuses mounted to the vehicle according to making and breaking of the electric continuity of the switching unit. For example, selection of lights and various modes of turning on and off of the lights can be switched selectively, such as the so-called automatic lighting for turning the light on and off automatically, turning a taillight on and off, and turning a headlight on and off.